Switching apparatus



Aug. 27, 1946.

C. C. WHITTAKER swITcHING APPARATUS Fil'ed June 29, 1944 n R ma n O Mw n A e B W l L c Patented Aug. 27, 1946 SWITCHIN G APPARATUS Charles C. Whittaker, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation'of Pennsylvania Application June 29, 1944, Serial No. 542,735

My invention relates, generally, to switching apparatus and, more particularly, to switches of the carbon-break type.

An object of my invention, generally stated, is to provide a carbon-break switch which shall be simple and eicient in operation and. which may be economically manufactured and installed.

A more specic object of my invention is to provide a carbon-break switch which opens an electric circuit in a multiple number of places simultaneously.

Another object of my invention is to provide for inserting a high resistance into an electric circuit before it is opened by a carbon-break switch.

A further object of my invention is to provide a carbon-break switch in which the carbon pile is shunted from the circuit while the switch is carrying current continuously.

Other objects of my invention will be explained Jfully hereinafter or will he apparent to those skilled in the art.

In accordance with one embodiment of my invention, certain of the carbon discs of a carbonbreak switch are deected to make contact at their edges when pressure is applied along the longitudinal axis. As the pressure increases, vthe resistance through the discs decreases, and nally the carbon pile is shunted from the circuit. When the pressure is decreased, the rst movement reinserts the carbon pile into the circuit while still compressed. As the pile expands, the resistance increases greatly and then the discs separate simultaneously at a plurality of diierent places, thereby providing a multiple-break switch.

For a fullerunderstanding of the nature and objects of my invention, referencel may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a view, partially in elevation and partially in section, of a switch embodying my invention.;

Fig. 2 is a view, in plan, of the switch shown in Fig. l, portions being broken away for clarity, and

3 is an enlarged View, in section, of a portion of the carbon pile utilized in the switch.

Referring to the drawing. the structure shown therein comprises a base I on which is mounted a carbon pile assembly I I, an air cylinder I2, and a magnet valve I3 for controlling the admission of compressed air to the cylinder I2 in the usual manner. The air cylinder I2 and magnet valve I3 may be of the conventional type and,

5 Claims. (Cl. ZIM-51)' therefore, will not be described in detail in the presentV application, An auxiliary or interlocking switch assembly Ill of the usual type may be mounted on the cylinder l 2, as shown.

An insulator I 5 is connected to the external end of the piston rod for the piston disposed in the cylinder I2. A metal yoke IS is connected to the insulator l5 by means of a bolt I1 and is therefore actuated by the piston in the cylinder i12. A flat metal plate I8 may be secured to the ends of the yoke I6. The plate I8 is utilized to apply pressure to the carbon pile assembly II and also to complete an electrical circuit to the carbon pile. The yoke I5 is connected to a fixed terminal I9 by means of a flexible shunt 2U.

The carbon pile assembly II comprises a plurality of carbon plates or discs ZI and 22 and insulating spacing washers 23. A flat metalend plate 24 is provided at one end of the carbon discs, and a iiat metal plate 25 is provided at the other end. The carbon discs ZI and 22, the insulating washers 23, and the metal plates 24 and 25 are all slidably mounted on a glass rod 26 which in turn is slidably mounted on a xed copper rod 2'1.

The copper rod 2i is supported at one end by an angle bracket 28 and at the other end by an angle bracket 29. The brackets 28 and 29 are secured to the base l0. A terminal connection 3! is secured to the end of the copper rod 2l which is mounted in the bracket 28, and the bracket 28 is electrically connected to the end plate 25 by means of a flexible shunt 32. The other end of the copper rod 2l may be silver tipped and is disposed to be engaged by the end ci the bolt II when the carbon pile is substantially fully compressed. The end of 'the bolt i'! may also be silver tipped.

The carbon discs are compressed against a spring which is disposed between the end plate '25 and the bracket 28. The glass rod 26 is compressed against a spring 34 which is disposed inside of the spring 33 between a metal sleeve 35 at the end of the rod 26 and the bracket 23.

As illustrated more clearly in Fig. 3, the carbon discs ZI are flat and each disc 22 is undercut slightly on each side as shown. Furthermore. the discs 2! are disposed in pairs with an insulating washer disposed between the discs of each pair. Each pair of the dat discs 2! is disposed between two of the undercut discs `22. Thus, when pressure is applied. on the discs, the wide portions of the undercut discs engage the ilat discs 2 I, thereby causing each pair of discs 2l to be deflected toward each other to make contact at their outer edges since their central portions are kept apart by the spacingr washers 23. As the pressure increases, the action is similar to that in the ordinary carbon pile resistor where the resistance decreases as the pressure increases.

Assuming that it is desired to close the switch, the magnet valve I3 is energized to admit air to the cylinder I2, thereby causing the yoke I6 to press the plate I8 against the end plate 24. When the edges of the carbon discs 2| make Contact, as described hereinbeiore, the electrical circuit is established through the carbon pile which at this time has a relatively high resistance. As the pressure on the carbon pile is increased, the resistance is gradually decreased until finally the contact member I1 engages the end of the copper rod 21. At this time, the switch is entirely closed, and the electrical circuit extends from the terminal I9 through the shunt 20, the yoke I6, the contact member I1, the copper rod 21, and the terminal 3l` Under this condition, the carbon pile is shunted from the electrical circuit. In this manner there are no losses in the carbon pile while the switch is carrying current continuously.

When it is desired to open the switch, the magnet valve I3y is deenergized to exhaust the air from the cylinder I2, thereby releasing the pressure on the carbon pile. The rst movement of the yoke I6 to the left opens the circuit through the contact member I1 and the rod 21, thereby inserting the carbon pile into the circuit while substantially fully compressed.

As the pressure, is removed, and the carbon pile expands, the resistance increases gradually until finally all of the carbon discs 2l separate simultaneously, thereby interrupting the electrical circuit at a multiple number of places. Since, as explained hereinbefore, the flat discs 2I make contact at their outside edges and also break contact at the same place, any arcs caused by interrupting the circuit are at the outside periphery of the carbon pile. When the switch is fully opened, a wide gap exists in the electrical circuit between the contact member I1 and the end of the copper rod 21.

From the foregoing description, it is apparent that I have provided a carbon-break switch which inserts a very high resistance into an electrical circuit when the circuit is opened, thereby reducing the current to almost zero and then opening the circuit in a multiple number of places simultaneously. It is evident that the switch herein described has numerous applications in the electrical field, such as, for example, in the control of electrically propelled vehicles, particularly those operating in mines where it is desirable to avoid the drawing of arcs during the opening of an electric circuit.

Since numerous changes may be made in the above-described construction, and diierent em- 4 bodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In an electric switch, in combination, a carbon pile having a plurality of undercut carbon discs and a plurality of pairs of ilat carbon discs disposed to make contact at their edges when compressed together to establish an electric circuit through the switch, each pair of ilat discs being disposed between two of the undercut discs, and spacing means disposed between certain of said discs to cause them to be deflected toward each other when compressed axially, said spacing means having a smaller diameter than said discs.

2. In an electric switch, in combination, a carbon pile comp-rising a plurality of undercut carbon discs and a plurality of pairs of flat carbon discs, the discs of each pair of iiat discs being disposed between two of, the. undercut discs to make contact at their edges when compressed together to establish an electric circuit through the switch, and a spacing washer disposed between the discs of each pair to cause them to be deflected toward each other when compressed axially, said spacing washer having a smaller diameter than said discs.

3. In an electric switch, in combination, a carbon pile comprising a plurality of pairs of flat carbon discs and a plurality of undercut discs, the discs of each pair of flat discs being disposed to make contact at their edges when compressed together between two of the undercut discs to establish an electric circuit through the switch, and means for compressing the carbon pile axially.

4. In an electric switch, in combination, a carbon pile comprising a plurality of pairs of ilat carbon dises and a plurality of undercut discs, the discs of each pair of flat discs being disposed to make Contact at their edges when compressed together between two of the undercut discs to establish an electric circuit through the switch, a spacing washer disposed between the discs of each pair of flat discs, and means for compressing the carbon pile axially.

5. In an electric switch, in combination, a carbon pile comprising a plurality of pairs of flat carbon discsl and a plurality of undercut discs, a spacing washer between the discs of each pair of flat dises, and means for compressing the discs of each pair of flat discs between two of the undercut discs against said washer to make contact at their edges to establish an electric circuit through the switch, said spacing washer having asmaller diameter than said discs.

CHARLES C. WHITTAKER. 

